.45 inch Martini Henry
Although the term .577/.450 inch has become the accepted norm for this cartridge, it is in fact a commercial name that reflects the fact that the head diameter is the same as the .577 inch Snider cartridge from which it was derived. In British military nomenclature the cartridge was only ever call the ".45 inch".
The origins of the round lie in the desire to move away from the Snider to a newly designed breech loading rifle. The calibre of the Snider had been fixed by that of the original muzzle loading Enfield rifle from which it was converted and it was recognised that .577 inch was far from ideal and that a calibre of about .45 inch was desirable.
A series of competitions were arranged by the War Office in the years 1866 to 1869 in which many inventors submitted designs for a new breech-loading rifle. These trials were often inconclusive, but by March 1869 a decision was made to produce 200 trial rifles using the Martini action wedded to the Henry barrel.
For the main trials in late 1869 a long straight cased .45 inch cartridge was used, of which there were two patterns, a Type " A" and a type "B", the latter being that used for the trials of the experimental Martini Henry rifle.
The principal difference between them was the type of powder used and the thickness of the iron base disc.
The .45 inch long chamber Type "A" cartridge had a straight case of rolled brass foil, 3.75 inches long and covered in brown paper. The joint between the base cup and the main body of the case was covered in a thin strip of white tissue paper. The base disc was of iron and was 0.030-0.035 inches thick.
The bullet was made of an alloy of 12 parts lead to 1 part tin and weighed 480 grains with a single cannelure. It was covered with a white paper patch.
The propellant charge was 85 grains of Waltham Abbey RMH blackpowder, Above the charge was a beeswax wad with one cardboard disc below and two above..
The Type "B" cartridge made to complete the trials of the experimental rifles. It was similar to the Type "A" but had a thicker base disc for strength, measuring 0.040-0.045 inches thick.
The bullet was identical but the propellant charge was 85 grains of Curtis & Harvey's No.6 powder, changed in May 1870 to Waltham Abbey "K" blackpowder. The beeswax wad was cupped on the top side and had the same cardboard discs as the Type "A".
Whilst the trials were taking place experiments were also conducted on a short case bottle necked round based on the patents of W.T.Eley. It is known that there was a design of short chamber case dated September 1869 but details have been lost. Design RL 767 is dated November 1869 and covered "Cartridge S.A. Ball Breech-Loading Boxer Henry for .45 inch Martini Henry Rifle Short Chamber 85 Grains". The design was sub-titled "Provisional Pattern B" thus inferring that the September 1869 design was "Pattern A".
The Pattern B used the same 480 grain bullet of the long chamber case and the charge was also 85 grains, presumably of the same Waltham Abbey powder. Subsequent to this, another design, RL810, was provisionally approved as "Cartridge S.A. Ball Breech-Loading Boxer Henry for .45 inch Martini Henry Rifle Short Chamber 85 Grains Mark I", although this differed in detail from the Mark I that was finally approved in April 1871. The differences are not known in detail but were probably minor, perhaps in the powder used or the type of wads.
Note: Air Service variants of the Martini Henry rounds are covered separately on their own page.